refactor(log): unify request lifecycle logging with session-colored tags

Collapse scattered per-request console lines (request/routing/auth/pending/
usage/stream-usage/stream) into 3 correlated lines: request, transform,
done. Add stable per-session color tag so concurrent request lines are
easy to follow, surface thinking intent, always-on full error logging
for debug, re-enable warn level, and uppercase keyword labels. Also fix
usage overview cards wrapping (5 cards -> grid-cols-5).

Co-authored-by: Cursor <cursoragent@cursor.com>

src/app/(dashboard)/dashboard/usage/components/OverviewCards.js

@@ -8,7 +8,7 @@ const fmtCost = (n) => `$${(n || 0).toFixed(2)}`;
 
 export default function OverviewCards({ stats }) {
   return (
-    <div className="grid min-w-0 grid-cols-1 gap-3 sm:grid-cols-2 md:grid-cols-2 lg:grid-cols-4 sm:gap-4">
+    <div className="grid min-w-0 grid-cols-1 gap-3 sm:grid-cols-2 md:grid-cols-3 lg:grid-cols-5 sm:gap-4">
       <Card className="flex min-w-0 flex-col gap-1 px-4 py-3">
         <span className="text-text-muted text-sm uppercase font-semibold">Total Requests</span>
         <span className="truncate text-2xl font-bold">{fmt(stats.totalRequests)}</span>